In a conventional server-client system of this type, reserve information of a device connected to a server is acquired as follows.
When a certain device, which is connected to a server system and is being used by a given client computer is accessed by another client computer in the same communication system, it is easy to inhibit the device from being used by the another client by indicating that the device is reserved or in use. Since the same communication system is used, all clients in the system can easily detect the states of devices as long as a system program holds information indicating that “a device is reserved or in use”.
However, whether or not a device in another communication system is reserved cannot be easily discriminated from this communication system. For example, when a device to be used is a scanner connected to another system via a SCSI I/F, it cannot be determined, based on a SCSI command, if that device is reserved by another system program of an identical computer, and a TWAIN driver that handles this scanner does not normally discriminate whether or not that scanner is reserved.
Therefore, a conventional server-client program cannot determine whether a device connected to a server system is being used by another program in the server system computer, and simultaneous accesses often produce invalid results. Also, when an error has occurred while the server-client program is using that device, and an error message is displayed on only the display screen of the server system, the users of the client systems cannot determine what has happened.
For example, when simultaneous accesses have taken place during use of the scanner as a shared device, the image scanning mode becomes indeterminate, or a scan is done in the mode which was last set and an image desirable for a given user but is not desirable for the other user is output.
When a device connected to the server system is not ready, for example, its power switch is OFF, and the operator of the client operates that device connected to the server system, a program for controlling the device, which is registered in the server system, displays an error message on the display screen of the server system, and waits for confirmation by the user. For this reason, the operator of the server system must go to the site of the server to check if any message pertaining to the device is displayed on the display screen of that server system by the program for operating the registered device. In this case, if the operator finds an error message dialog displayed on the server, the operator must confirm and close the dialog window.
Therefore, in the conventional server-client program, when a device connected to the server system is not ready, the program for operating the device registered in the server system displays an error message on the server system, but no information is returned to the client system, and the client operator cannot determine what has happened.
Conventionally, when a client connected to the network scans an image using an image input device on the server side, some application software programs that start up the image input device do not display any window. In general, when a window is displayed, such mode is called a UI (User Interface) mode; when no window is displayed, such mode is called a UI-less mode (windowless mode). Most OCR application software programs and the like run in the UI-less mode.
For this reason, when a client scans an image using the image input device at the server side, if the scan control (driver) of the image input device used runs in the UI mode, a predetermined UI dialog is displayed only on the server, and no information is returned to the client, resulting in poor operability.